This invention relates to semiconductor processing equipment. More specifically, it relates to kinematic coupling of substrate carriers to processing equipment.
Generally, substrate carriers, for example, 300 mm wafer containers, known as FOUPS (acronym for front opening unified pod) and FOSBS (acronym for front opening shipping container) include a downward facing equipment interface portion, such as a guide plate, that has a kinematic coupling, for properly orienting the carrier with respect to carrier interface portions provided by the processing equipment. The configuration of the equipment interface portions are typically dictated by industry standards promulgated by the Semiconductor Equipment and Materials International (SEMI). For 300 mm wafer containers the equipment interface located on the bottom of the containers are known as kinematic couplings. Other equipment interfaces may also exist on substrate carriers. Some substrate carriers have equipment interface structures 10 configured as the kinematic couplings that are integrated into the same mold as a container portion of the carrier. Other substrate carriers utilize a mounting plate 20 that is molded apart from and subsequently attached to a carrier, as shown in FIG. 2. Still other substrate carriers, such as those depicted in U.S. Pat. No. 6,520,338, which is hereby incorporated by reference, utilize a guide plate 30, as shown in FIG. 3, to center contact of the processing equipment onto partitions that extend directly from the exterior surface of the substrate carrier. The portions of the structure that interface with the external processing equipment can be molded integrally with the mounting plate or guide plate, overmolded onto a base structure, or formed separately and attached to the base structure.
Typically, a guide plate or kinematic coupling plate will have a trio of grooves with inclined walls arranged equilaterally about a central axis, with the apex axis of each groove oriented to intersect with the central axis. The process equipment typically engages the inclined surfaces of the groove with mounting pins to provide a stable three-point mount.
The purpose of the kinematic couplings is to provide a stable and repeatable means of positioning the carrier and the substrates within the carrier at a predetermined height for robotic manipulation. If the carrier is not located at a tolerable height or orientation with respect to the processing equipment, the robotic manipulators may malfunction, causing delays in the assembly line as well as damage to the substrates or carrier. A common problem encountered with the kinematic couplings is that the interface portions will sometimes frictionally adhere or “stick” to the contacting surfaces of the processing equipment. If the sticking occurs before the carrier is stably seated on the mounting pins, the carrier may “hang up” and remain at an unacceptable height, or cause the carrier to list at an intolerable angle with respect to the robotic manipulators. Also, as the robotic manipulators begin to handle the substrates, the carrier may suddenly slip off the stick point, causing the carrier to lurch downward and causing a risk of damaging contact between the robotic manipulators and the substrates.